A microcapsule is a substantially spherical object, which consists of a core and a wall (shell) material surrounding the core, wherein the core may be a solid, liquid or a gaseous component. For many applications the wall (shell) is formed by a polymer material. Microcapsules usually have a volume average diameter from 1 to 1000 μm.
A multitude of shell materials is known for producing the wall (shell) of microcapsules. The shell can consist either of natural, semisynthetic or synthetic materials. Natural shell materials are, for example, gum arabic, agar agar, agarose, maltodextrins, alginic acid or its salts, e.g. sodium alginate or calcium alginate, fats and fatty acids, cetyl alcohol, collagen, chitosan, lecithins, gelatin, albumin, shellac, polysaccharides, such as starch or dextran, polypeptides, protein hydrolyzates, sucrose and waxes. Semisynthetic shell materials are inter alia chemically modified celluloses, in particular cellulose esters and cellulose ethers, e.g. cellulose acetate, ethyl cellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and carboxymethylcellulose, and also starch derivatives, in particular starch ethers and starch esters. Synthetic shell materials are, for example, polymers, such as polyacrylates, polyamides, polyvinyl alcohol, polyvinylpyrrolidone, polyurea, polyurethane or aminoplast.
Polyurea core-shell microcapsules are of interest for home care, personal care and household care applications. To assure their adoption in these applications, they must exhibit deposition and adhesion properties on the substrate, such as textile, skin, hair, leaf or other surfaces.
It is known that positively charged microcapsules exhibit enhanced deposition when applied to a situs, such as fabric. Indeed, coating materials that are applied to microcapsules in order to impart a positive charge are sometimes referred to as “deposition aids”.
Several prior art documents disclose cationic microcapsules, in particular polyurea core-shell microcapsules.
WO 01/62376 relates to microcapsules, wherein the surface of these microcapsules has a positive charge. The positive charge is created either by selecting wall (shell)-forming materials that are positively charged, or by modifying the capsule wall (shell) by applying a surface coating of a cationic compound, e.g. quaternary ammonium compounds, cationic polymers or emulsifiers.
WO 2011/123730 describes a process for coating microcapsules with a cationic polymer, wherein a sufficient amount of a cationic polymer is added to negatively charged pre-formed microcapsules in order to obtain a surface-modified microcapsule bearing a positive zeta potential.
US 2012/0148644 relates to polyurethane or polyurea microcapsules, which may be modified with a polymer, which is selected from an amphoteric or a cationic polymer, such as polyquaternium-6, polyquaternium-47, polyvinylamine and its copolymers with vinylformamide.
U.S. Pat. No. 8,426,353 relates to perfume-containing polyurea microcapsules. The microcapsules are obtained from a mixture of polyisocyanates and a colloidal stabilizer which is an aqueous solution of a polyvinyl alcohol and of a cationic copolymer of vinylpyrrolidone and of a quaternized vinylimidazol. The polyisocyanates and the polyvinyl alcohol react together while the cationic copolymer can be easily removed. Indeed, the cationic copolymer is non-covalently bound to the capsule shell and thus is easily washed off from the capsule wall (shell) during the manufacture.
Despite the extensive literature devoted to the provision of encapsulated perfumery, there is currently no commercially acceptable encapsulated perfume composition that is easy to manufacture, stable and provides good deposition while delivering good olfactive performance.